Rolling zinc-base alloy



United States Patent 3,113,053 RQLHNG ZENQ BASE ALLOY Carl M. Zvanut, Alton, lll., assignor to The Dow Chemical Ccinpany, Midland, Mich a corporation of Delawere No Drawing. Filed Mar. 2, 1961, Ser. No. 92,743 5 Claims. (Cl. 148-415) The invention relates to the rolling of zinc-base alloy and more particularly relates to an improved method of rolling zinc-base alloys containing both copper and titanium.

Heretofore zinc-base alloys have been cast in relatively small slabs, e.g., 1% X7x 14 inches, heated to at least 410 F., and rolled utilizing hot rolls. Rolls heated to 150 to 300 F. have been used for rough rolling, i.e., initial rolling to reduce the thickness of the slab to sheet metal proportions; and rolls heated to about 250 to 300 F. have been used in finish rolling the sheet metal to further reduce the thickness of the sheet metal under conditions whereby desirable physical properties are developed in the sheet metal and the surface of the sheet is erfected substantially free of defects such as roll markings.

lowever, in rolling relatively large slabs of zinc-base alloy, e.g., x 40 x 80 inches, large rolls are used which are not so readily heated and maintained at the elevated temperatures previously used in finish rolling. And if cold rolls are used in the above-described rolling process, the physical strength properties of the metal are not fully developed.

It is therefore a principal object of the present invention to provide a method of rolling large slabs of zincbase alloy, particularly the zinc-base alloys containing copper and titanium.

Another object of the invention is to provide a method of rolling zinc-base alloy, containing copper and titanium, with cold rolls.

Another object of the invention is to provide a method of roiling zinc-base alloy, containing copper and titanium, whereby the rolled metal exhibits good bend ductility, i.e., can be bent across a very short radius without cracking the metal.

Still a further object of the invention is to provide a method of rolling Zinc-base alloy through cold rolls (cooler than 140 F.) whereby the surface of the rolled metal is substantially unmarred by the rolls.

These and other objects and advantages of the present invention will be more fully understood by those skilled in the art upon becoming familiar with the following description and the appended claims.

The invention is predicated on the discovery that upon rolling zinc-base alloy containing both copper and titanium to sheet form with cold rolls using an annealing temperature of at least 400 F. between passes through the rolls, and a final pass entry temperature of at least 400 F., the so-rolled sheet metal exhibits consistently high hardness, good creep resistance and improved bend ductility.

Zinc-base alloys advantageously rolled according to the method of the invention are those containing by Weight about 0.1 to 2 percent of copper, 0.05 to 0.5 percent of titanium, and the balance substantially commercial zinc.

In carrying out the method of the invention an ingot or rolling stab or zinc-base alloy is generally heated to a temperature of 400 to 550 F. or higher, if desired, and rough rolled in any suitable manner to reduce the thickness of the metal. Thus the metal may be heated and rolled repeatedly through hot rolls as understood in the art, or it may be passed repeatedly through cold rolls, reheating to at least 400 F. between most passes or between each pass. The so-prepared sheet metal is then ice finished rolled one or more times, including at least the terminal or ultimate pass, the procedure per pass being as follows: the sheet metal is heated to a temperature in the range of about 400 to 550 F., then while the temperature of the metal is at least 400 F. it is passed between cold rolls maintained at a temperature of to F., or cooler, if desired, under the requisite roll pressure to cause about 25 to 60 percent reduction, the metal exiting from the rolls at a temperature in the range of 200 to 400 F. preferably below about 375 F., and more preferably below about 300 F. Under these conditions of rolling the physical properties of a zinc-base alloy containing copper and titanium are substantially optimized without the use of a final annealing step as in the prior art.

While a final annealing step is thus unnecessary to improve the creep resistance and physical strength properties of the alloy, it is sometimes desirable to thermally flatten sheet metal which has been coiled as it leaves the rolls of the mill. If desired, the sheet metal rolled according to the invention may be cut into suitable lengths, stacked and weighted down and placed in an oven and heat treated at temperatures in the range of 200 to 300 F. for an hour without adversely aitecting the physical properties of the metal.

To avoid surface marking of the sheet metal on its being passed through cold rolls according to the method of the invention it has been found very desirable to flood the rolls with a lubricant such as a mechanical emulsion of lard oil in water. The emulsion lubricates the rolls thus preventing marking of the metal being rolled. Use of the emulsion also helps to keep the rolls cool during contact with hot sheet metal.

Example 1 A zinc-base alloy having the composition by weight 0.82 percent of copper, 0.12 percent of titanium, the balance commercial zinc, was cast into a rolling slab having the dimensions 10x40x80 inches. The slab was heated to about 420 F., reduced to sheet metal 0.180 inch thick by passing the hot metal through the rolls of a mill 21 times, and coiled. The coiled metal was reheated and further rolled as follows:

Reheat Initial Final Exit Additional pass Temp, F. Thickness, Thickness, Temp., F.

in. in.

A roll temperature of 130140 F. was maintained throughout the entire rolling sequence.

Coupons were cut from the so-rolled sheet and tested for the minimum radius of 180 bend which did not result in cracking of the metal. It was found that the coupons would accept a 2T bend, i.e., could be bent 180 back on itself without cracking the metal. On further testing the rolled zinc alloy sheet was found to exhibit a hardness of 65 on the R 15 T scale (A.S.M.).

Example 2 A zinc-base alloy having the composition by weight 0.25 percent of copper, 0.1 percent of titanium, and the balance zinc, was prepared and processed according to the invention in the same manner as the alloy of Example 1. The so-rolled sheet accepted a 2T bend without cracking and exhibited a hardness of slightly greater than 60 on the R 15 T scale.

Example 3 A zinc-base alloy having the composition by weight 0.45 percent of copper, 0.1 percent of titanium, and the balance zinc, was prepared and processed according to the invention in the same manner as the alloy of Example 1. The so-rolled sheet accepted a 2T bend without cracking and exhibited a hardness of slightly greater than 60 on the R 15 T scale.

Comparison By way of comparison, a zinc-base alloy having the composition by weight 1.0 percent of copper, 0.12 percent of titanium, and the balance zinc, Was cast into a rolling slab having the dimensions 1% x7x14inches. The slab was heated to about 350 F. and reduced in thickness to 0.09 inch in 11 passes through heated rolls (250 F.). The so-rolled metal was heated to 300 F. and finish hot rolled (140 F. rolls) to a thickness of 0.018 inch in 3 passes through the rolls of the mill. The final exit temperature was 415 F. Coupons cut from the so-rolled metal would not accept less than a 3-4T bend, i.e., would not accept a 180 bend on itself (2T) but required bending 180 around 12 thicknesses of the same gauge metal (3-4T).

Among the advantages of the invention are the improved bend ductility provided in the rolled metal, and the simplifying of the metal preparation in making a final annealing step for the improvement of properties unnecessary.

The method of the invention thus being described, obvious modifications apparent to those skilled in the art are to be considered within the spirit of the invention the scope of which is to be considered limited only by the appended claims.

I claim:

1. The improved method of finish rolling sheet metal formed of zinc-base alloy containing from about .1 to 2 percent by weight of copper, and 0.05 to 0.5 percent by weight of titanium the balance substantially zinc which comprises: heating and rolling the sheet at least once, including the terminal pass through the rolls of a mill, as follows: annealing the sheet at a temperature in the range of 400 to 550 F.; and passing the annealed sheet through cold rolls of a mill at the requisite roll pressure whereby the thickness of the annealed sheet is reduced by about 25 to 60 percent, the temperature of the sheet entering the rolls being in the range of 400 to 550 F., the temperature of the sheet exiting from the rolls being below about 375 F., and the temperature of the cold rolls being maintained at about 125 to 140 F.

. 2. The improved method of finish rolling sheet metal as in claim 1 in which the annealed sheet is reduced by about 40 to 60 percent.

3. The improved method of finish rolling sheet metal as in claim 1 in which the sheet temperature of the metal exiting from the rolls is below about 300 F.

4. The improved method of rolling sheet metal formed of zinc-base alloy containing 0.1 to 2 percent by weight of copper, 0.05 to 0.5 percent by weight of titanium, the balance substantially zinc, which comprises: heating the alloy to a temperature in the range of from 400-550 F. passing the so-heated metal a plurality of times through the rolls of a mill whereby the thickness of the metal is reduced, and finish rolling the so-prepared sheet at least once, including the terminal pass through the rolls of a mill, as follows: annealing the sheet at a temperature in the range of 400 to 550 F.; and passing the annealed sheet through cold rolls of a mill at the requisite roll pressure whereby the thickness of the annealed sheet is reduced by about 25 to percent, the temperature of the sheet entering the rolls being in the range of 400 to 550 F., the temperature of the sheet exiting from the rolls being below about 375 F., and the temperature of the cold rolls being maintained at about to F.

5. In the improved method of rolling sheet metal formed of a zinc base alloy containing from about .1 to 2 percent by weight of copper, and 0.05 to 0.5 percent by weight of titanium the balance substantially zinc in which the alloy is initially subjected to a rough rolling process according to which the metal is heated to a temperature of 400 to 550 F., and passed through rolls of a mill a plurality of times, reheated to at least 400 F. at least once and further passed through the rolls of a mill, and subjected to a finish rolling process, the improved finish rolling process which comprises: heating and rolling the sheet at least once, including the terminal pass through the rolls of a mill, as follows: annealing the sheet at a temperature in the range of 400 to 550 F.; and passing the annealed sheet through cold rolls of a mill at the requisite roll pressure whereby the thickness of the annealed sheet is reduced by about 25 to 60 percent, the temperature of the sheet entering the rolls being in the range of 400 to 550 F., the temperature of the sheet exiting from the rolls being below about 375 F., and the temperature of the cold rolls being maintained at about 125 to 140 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,472,402 Boyle June 7, 1949 2,516,737 Wilson July 25, 1950 FOREIGN PATENTS 343,042 Great Britain Aug. 9, 1929 

1. THE IMPROVED METHOD OF FINISH ROLLING SHEET METAL FORMED OF ZINC-BASE ALLOY CONTAINING FROM ABOUT .1 TO 2 PERCENT BY WEIGHT OF COPPER, AND 0.05 TO 0.5 PERCENT BY WEIGHT OF TITANIUM THE BALANCE SUBSTANTIALLY ZINC WHICH COMPRISES: HEATING AND ROLLING THE SHEET AT LEAST ONCE, INCLUDING THE TERMINAL PASS THROUGH THE ROLLS OF A MILL, AS FOLLOWS: ANNEALING THE SHEET AT A TEMPERATURE IN THE RANGE OF 400 TO 550*F.; AND PASSING THE ANNEALED SHEET THROUGH COLD ROLLS OF A MILL AT THE REQUISITE ROLL PRESSURE WHEREBY THE THICKNESS OF THE ANNEALED SHEET IS REDUCED BY ABOUT 25 TO 60 PERCENT, THE TEMPERATURE OF THE SHEET ENTERING THE ROLLS BEING IN THE RANGE OF 400 TO 550*F., THE TEMPERATURE OF THE SHEET EXITING FROM THE ROLLS BEING BELOW ABOUT 375*F., AND THE TEMPERATURE OF THE COLD ROLLS BEING MAINTAINED AT ABOUT 125 TO 140*F. 